text:
Could a shrouded fan blade with long chord length be efficient?
I am wondering if it would work to have a fan with two or three blades which have short-ish span and very long chord length, like half a rotation for each blade. Would a shroud (that is molded on the tip of the blades) create/solve any problems?
I am also thinking about tandem blades, but that would only work with shorter chord lengths, correct?
The main objective is to keep noise to a minimum.
I have no background in aerodynamics, just been reading up about it for a while. So please try to dumb it down where possible.
Edit: this is what I came up with, taking all the advice I've received so far.
https://www.thingiverse.com/thing:4069048
Any ideas on improvements?

You should transform the title in a question as this is standard in this Q&A website.

Related: https://aviation.stackexchange.com/q/67177

Early jet fan blades are just like that, long and narrow, but it turns out they are fragile and vulnerable to bird strike, so the industry moved to wider blades.

@Rudi, what is your overall objective?  (Besides noise reduction)  Are you designing a jet engine?

@Michael Hall, I am designing a quiet desktop fan blade that still moves a descent amount of air. I plan to power it either with a 2 pole (2900 rpm) or 4 pole (1450 rpm) ac induction motor, depending on what speed I need.

The main objective of the engine is to generate required power $\text{P}$, which is:
$$\text{F} \times \frac{D}{T}$$
where $F$ is force, $D$ is distance, and $T$ is time.
Power generated by modern jets through continuous combustion of fuel dwarfs their piston predecessors.
Next up is efficiency. As in wings, longer, thinner blades do a better job converting this power. A typical measurement is the thrust-specific fuel consumption:
$$\frac{g}{(s \cdot kN)}$$
which is fuel flow (fuel over time) per thrust.
Piston engines went from 2 to 3 to 4 blades, enabling more thrust output, but the "wake", or turbulence generated from one blade lowers the efficiency of the next one following it. 1 blade is most efficient, but to get more thrust from the more powerful engines, some efficiency is sacrificed. Fan jets follow this trend with many blades.
But short blades with a very long chord would be hopelessly inefficient for generating thrust in air. A very good example of this thinking is the modern windmill design, with fewer, longer blades than the old style mills. The faster you turn, the more you want to be like the modern mill. The turboprop makes the most of propeller efficiency and turbine power but:
All types of props or ducted fans reach a speed limit where their own drag makes them less efficient than low bypass turbojets. Propellers reach this limit before fans do, which is why we see fans on longer range airliners.
So we did not get to noise reduction with this concept, which is relegated to desk top fans.
Modern jets do have some success with noise reduction by controlling their fan blade tip speeds, and by improving the design of their containment housings (nacelles).

Thanks for all the info. So I now understand that a long chord would not be worthwhile in this situation. Would it work if I tried something like this: https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQEePhNi-YtR82U9O2pN4R8wzF2mOs5sdhe-D463BkJlTpCyqTI I keep thinking that the shroud would help a lot with noise reduction and this is my biggest objective.

@Rudi certainly worth a try, it may improve thrust output as well (acting as a running blade (airfoil) tip "fence"), and thanks to ymb1 for edits.

@Rudi especially if you could recess the ring into a groove in the nacelle airflow intake, which could effectively eliminate the "gap" between the blade tips and the intake wall.  Stay on it.

This is what I came up with so far https://www.thingiverse.com/thing:4069048


text:
why some airplanes have their exhaust gases vectored above the wing?
I was looking at images of the SkyCourier shown below

and i have noticed the asymmetrical exhaust pipes in both engines (one pointing up and one is straight), doing my research on the internet, i found that it is used to take advantage of the Coanda effect and the flaps so that the gas moves from the top side of the wing and then gets deflected downward for a high lift effect in takeoff...
Yet i believe you can get the same effect if the gases were vectored under the wing and made hit the flaps, so why would they vector the gases above the wing, and why the second exhaust is not deflected upward ?

I suspect the benefit is mostly theoretical. It would be interesting to see actual test data that showed a significant difference.  One big problem with running exhaust over the wing like that is the heat plays havoc with the structure.  DeHavilland Dash 7s had a problem with the top exhaust actually annealing the 7075 alloy upper skin planks, causing wrinkling, and required insulating doubler panels to be added in the field.

@JohnK I'm sure the designers of the AN-72/74, YC-14 and C-17 will not agree with "the benefit is mostly theoretical"

Those are turbo fans that are using primary thrust flow.  A small turboprop has very little velocity energy coming from its exhaust.

I'm not so sure that it's not on both sides, one of the exhaust ports points up, the other is straight. I think the set up is the same on both sides of that aircraft, so the person is blocking the upward directed exhaust on the right side.

hi Ron, i mean in the same engine , one of the exhaust pipes is straight and the other points up ...

The effect of the propeller wash would completely dominate any thrust related effects on lift.  On TBPs with large propellers the variation in sink rate is instantaneous with power changes.  The effect of the exhaust will be minor, and "lost in the noise" so to speak.  The other issue is the carbon deposits from the exhaust are bad for the wing structure, carbon and alum being galvanically opposed, so it's not a good idea to have exhaust impinge directly on the wing.  Operators will get a rude surprise during inspections 10000 hrs down the road.

Don't get the reference "the Canada effect"

@Super not "Canada", but "Coanda". The tendency of a fluid to follow a curved surface. https://en.wikipedia.org/wiki/Coand%C4%83_effect

Assuming that both props are rotating clockwise as seen from the rear, the orientation of the exhaust pipes makes sense if the goal is to ensure that the exhaust gasses are kept clear of the wing.
The rotating propwash will tend to carry the exhaust from the right-side pipe (in rear view) of each engine well below the wing.  If the left-side exhaust pipes were similarly positioned, their exhaust would be carried up by the propwash to impinge directly on the wing.  The position we see in the photo helps ensure that the propwash carries the exhaust from the left-side exhaust pipe of each engine well above the wing.
A comment from another ASE member (John K) has stated that exhaust impinging directly on the wing can lead to galvanic corrosion due to carbon deposits.

So the purpose is not to take advantage of the coanda effect , instead it is totally the opposite , they are trying to deflect the exhaust gases away from the wing?

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
What is this plane doing flying back and forth near Sydney at night?
As I write this, a mystery plane is going back and forth over south Sydney, Australia:

The plane took of at Bankstown, flies straight from West to East and back, with a distance between paths of about 600m. It maintains a steady height of ca. 4100ft at a speed 120kts.
It is a Cessna 404, but flightradar24 provides no call sign or any other ID.
I noticed the plane ca. 00:30 on 10 May 2018, as it was at its 8th "lap", and took the above screen shot. It may have gone on for a while, perhaps for an hour or more.
As it's night, no markings on the plane are visible. It has the usual white flashers on the wing tips and the top of the rudder, and the red and green marker lights. The plane is quiet loud (prop), but that's most likely only because it's night and there's no other sound sources in my suburb.
Does anyone have an idea what that plane could be, and what the purpose of such flights could be? Obviously, they (whoever they may be) waited until after the curfew of Kingsford Smith (23:00) to not get in the way of commercial traffic.
Might be similar to this question, but I have no way of knowing whether it is the same. Italy and Australia are different countries. E.g., to my knowledge, Europe doesn't permit Police planes or helicopters above urban areas without reason. Australia does.

These patterns are often for aerial photography, mapping, or occasionally, search and rescue operations.

@abelenky Photography at night? That scares me. The only ones who I can think of would engage in infrared photography at night are law enforcement. You know, trying to find cannabis plantations inside buildings...

@ymb1 Thanks, I'll do that next time.

Night time surveys are often preferable because there won't be moving traffic and all the activity of the daytime.   Its not necessarily color photography nor infrared.  LIDAR (laser surveys of elevation) are a prime example of a survey best done at night.

@abelenky Also, night air is often calmer and the ambient temperature is cooler, providing a more beneficial environment for e.g. LIDAR and IR surveys, where the plane‘s altitude must be kept rock steady.

@ymb1: Or you could just leave them there, or, alternatively, have so many tabs open at once that it's impossible to read what they are...

With a path like that its most likely surveying something. There are a handful of 404's registered in Australia for areal survey, you can find them on this list.

Interesting link, thanks a lot. I'd pay real money to know exactly what they are surveying in the suburbs.

They could be doing anything, Radar for topographic maps, checking GPS reception, light pollution survey etc etc.

If it's light pollution, I'm all in for this kind of stuff. There's way too many street lights, buildings illuminated nonsensically etc. Is GPS reception at 4100ft meaningful for GPS reception on ground level?

I rely on GPS more at 4100Ft. than I do at ground level... (comments are generally not for back and fourth but Id be happy to discuss this more in the chat )

Flights that have that kind of pattern are usually doing some kind of aerial photography.  Another possibility is that the plane could be collecting LIDAR data to get a 3D model of the city.  Sometimes planes are hired by the cell phone companies to scout good places to put a cell tower.  There could be any number of reasons that someone would fly parallel pattern route.

Thanks for the answer. Wouldn't it be better to get a 3D model straight from the building registrations etc? They would know exactly where each building is, the sizes etc. Unless they want the ground shape, of course. A new mobile phone tower on the other hand would really be in order. Reception sucks here...

@Lorca contacting all the right groups for that information would probably be a lot of work, and the data may not be that precise or even accurate. It's also possible that the municipalities get their information from this sort of survey.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Difference between engine rev up and run-up
Explain please the difference between these jet engine terms:

rev up
run up

Obviously they are completely different procedures. The reason I ask this question is because I'm not a native speaker and have some problems differentiating these 2 things.
You don't necessarily have to go deeply into technical details about these two procedures, however it would be welcomed ;)

I've never heard of engine rev up.

In english revving an engine is another way of saying "hit the throttle" while a run up is a pre-takeoff procedure the majority of uses for these terms is with piston engines. Can you supply some more context to your question?

As a non-native speaker, this would have probably been a better fit at [ELL.se], even though you got a fine answer here.

In general English usage, including in aviation, "rev up" is a verb form describing the act of increasing the speed of something.  "Rev up the engine" just means give it a shot of power to make it go faster.
"Run up", as used in this case, is actually a noun, describing a procedure to test an engine against go-no-go criteria.  "Do an engine run-up" means perform the run-up procedure, which may include accelerating the engine to a specific speed to put things under a bit of stress, and testing various systems while at speed to detect degraded or failed components or subsystems that are revealed only when under stress.


text:
Airport Security Pre-1970-s?
I just accidentally discovered a few pictures on the web, that seem to imply, that there were some sort of airport security checks on passengers all the way back in the 1960-s. It was always my general understanding that airport security screening was not a thing before the Hague and Montreal conventions in the early seventies and the various national regulations that followed, so I was really quite surprised about the photos, but I have a suspicion that they could be dated incorrectly or the descriptions might be wrong.
For example, here is a press article photo, of what apparently is an early metal detector.
The description on the back of it clearly says that this device is to replace searching of passengers at the airport. Does that mean that all the passengers boarding aircraft were searched in some other way before that?
Here is another picture that left me puzzled.
It seems to be taken at Zurich Kloten airport, with passengers queueing for some booths, where, they will be "inquired on weapons". What does that mean, what is happening inside those things? Was there some kind of security procedure, exclusive to Swissair flights, or to the Swiss airports? If such a thing existed, when did they drop that, in favor of the normal screening? Those "ladies" and "gentlemen" signs look really weird...
And one more picture.
The uploader claims they found it on the Atlanta airport website, which then claimed this was a test of some airport security machine as early as the year 1960! I mean that was before the first hijacking of a commercial flight in the US, if I am not mistaken!
I think this one could probably be fake or a joke, or just something irrelevant to airport security. I do not think I see any electronic equipment here except for the data logger in the front, yet judging by the way the people are dressed this seems to be taken in the sixties, even though I am no fashion expert. The picture circulates in the web with this description, but I could not find any more information on it. And that just makes me even more interested to know what is actually happening there.
If anyone knows what these things are all about, and how it used to work back then, I would absolutely love to hear that. So any explanations strongly appreciated!
Thank You!

Welcome to aviation.SE! If you don't get a good answer here you might also try travel.SE; passenger security screening is often off-topic here because it's more about traveling by air than about aviation. But let's see what others think.

@Pondlife It's at best borderline for Travel.SE, as it's about historical practices in the industry as opposed to anything that would help solve a practical, real-life problem for a current-day traveler. By analogy it would be like asking SO what pre-ALGOL coding standards were like in the 1950s. It's "interesting" but not "on-topic."

@choster I'm not very familiar with travel.SE so thanks for the information! This question might be off-topic on both sites; we usually close questions on passenger security screening because they have so little relevance to aircraft operations.

This has no connection in any way to Travel.SE.

This is not a question about "how-to passenger security screening" (as in "Can I carry aspirin?"), it's about historical airport practices.

Other airport questions have been answered here and the FAA seems to have been involved in early regulations so Id say this is in scope here.
Airport security is a bit older than the 70's. The first serious criminal  aviation incident occurred in 1955 but hijacking has occurred since the dawn of aviation with cases being recorded as far back as 1930. The first serious increase in security appears to have come in 1961 (bolding my emphasis)

Antulio Ramirez Ortiz hijacks a National Airlines flight to Cuba after
  it takes off in Florida. It is the first aerial hijacking of a U.S.
  passenger plane.
The U.S. government begins placing armed guards on commercial planes
  when requested by airlines or the FBI.

If you follow the citation in the metal detector wiki it sounds like the FAA started to make mandates in the early 70's following the DB copper incident but it clear things were happening before then.

But sky marshals couldn't ride on every flight, and the hijackings
  didn't end. So in December 1972, the FAA gave the airlines one month
  to begin searching all passengers and their bags. Dennis O'Madigan,
  then Director of Security for Piedmont Airlines, says metal detectors
  known as magnetometers were rigged up from a device originally used by
  loggers.

You should also keep in mind that in the earlier days of aviation ticket prices were extremely high and traveling via air was not as accessible as it is today thus some level of security was closer to what we see on private jets today. As ticket prices came down and the popularity grew greatly security became more of a concern.
On a similar note airport security has varied over time around the world. El Al the flagship carrier for Israle has generally implements security well above what most others are doing.

As for your pictures, the first one is dated 1970 which is in line with the timeline following the slew of incidents in the late 60's and the FAA's mandate of metal detectors in 72. The second picture is a bit of a mystery, it could be mis-labeled or they could simply be asking about weapons leaving the country as Switzerland historically has fairly liberal firearm laws and many other countries do not. The third photo looks staged or like a special situation, you can even see another photographer in the background. The Woman may in some way be famous (I cant identify her) and appears to be posing. That also looks like an EKG or polygraph machine...

Well, as you said yourself, early airline security was much more focused on law enforcement presence and dealing with hijackers, as opposed to screening all the passengers to prevent things. Still I do not believe, and I think the previous answer pretty much confirms this, there was some kind of screening for everyone universally.

I heard that some American airports and airlines screened select passengers, who would behave too suspiciously, at their own initiative, in the few years before it was mandated for everybody. Probably similar things happened in other places... But still I am pretty sure that was not before the age of metal detectors being used to screen people. So I am puzzled with regards to what "will replace the searching of passengers" means

Regarding the Swiss picture, asking questions about things is precisely how I would normally understand "inquiries", but why would they do that in enclosed cubicles, with the signs for ladies and gentlemen, separately? The nearby "toilets" sign seems to be pointing elsewhere :))

It seems that Swiss airports started deploying police officers to meet passengers at the airstairs immediately prior to them boarding their flights, and look for the clues, such as suspicious behavior circa 1969. Then soon after the Dowson Field, where one of the planes was a Swissair flight, they went on to screen everyone. I still could not find any more information on what that screening would look like in practice.

I would say that it was a situation where different airport authorities started to implement procedures on their own starting in the late 60s when the hijacking trade was getting started, and the conventions were adopted later to implement uniform security standards worldwide.

I traveled ( in the US ) in the 60's and remember the only check was for a ticket and that you were not trying to carry on a large suitcase. I remember some security checks starting in the late 70's after a few hijackings by Cubans. Then came the Muslims.

Apologizing in advance for any lack of political correctness.

Air travel was much more enjoyable back then , and easy, essentially no security as today. In about 1968 I was in Philadelphia ( traveling to Chicago) with my boss , he knew how to travel, he had a "million mile " plaque. from American . We were one hour early for our flight  , so instead of wasting that hour , he got out his schedule and said "Follow me ". We ran through the terminal to Braniff (?) , showed them our American tickets and got on about 5 minutes before departure.

What you are describing is pretty much exactly the image I have in my head about this, so when I found these little references to the passengers being searched before the introduction of metal detectors, I started wondering if my impression was wrong. I am curious what those pictures are about if universal passenger screening was not a thing even in the late sixties.

I think it is likely that Europe had more security sooner. I am certain El Al did.

The pictures are dated December October 1970. That would suggest that these new measures were introduced in response to the Dowson Field incident in September that year. https://www.gettyimages.co.uk/license/788214337 https://www.gettyimages.co.uk/license/788214341 https://www.gettyimages.co.uk/detail/photo/new-metal-detectors-at-heathrow-high-res-stock-photography/82573872 These three pictures all taken at Heathrow, also show that passenger screening was introduced probably within mere days after the Dowson Field. So, it was, indeed, a few years before the US.

Also I have just tried to translate the original French text on the Orly photo and it appears that the English description is inaccurate. The original says something like "in order to avoid disgusting traditional searches of passengers, who are suspected of carrying weapons, the security services now want to introduce this new piece of equipment"... To me that does not imply that such searches were actually happening at the time, just that they wanted to avoid resorting to them


text:
Why do slats deploy first?
I know on the 737, the leading edge slats deploy at the first flap setting, and the trailing edge flaps deploy after that at higher flaps settings. Why do the slats deploy before the trailing edge flaps?
LE Flap and slat schedule as it relates to TE Flap position for the 737-300:

The slats help to protect the outer wing from stalling when the flaps deploy. The outer wing carries the ailerons, so there are no flaps, but the flaps inboard will induce more lift on the whole wing, raising the effective angle of attack even in the aileron section. Slats push the stall angle of attack up. Without the protection provided by the slats, the outer wing could stall, and if this happens on one wing first (very likely, there are many reasons for flow asymmetry), the aircraft will roll violently. To do so during an approach is not good at all.
Look at aircraft with powerful flaps: They all have slats at least on the outboard wing to avoid outer wing stall. One goes with the other.

Why could the outer wing stall when the flaps inboard are extended? Is it due to the spanwise airflow to the wing tips in the sweep back?

@lemonincider: No, the increased lift inboard increases the induced angle of attack on the outer wing and lets its unmodified airfoil stall. Happens with a straight wing, too. I'm sorry if that sounds too similar to the answer itself - maybe ask a new question specifically with the part of the explanation that is unclear.

I've created a new question: https://aviation.stackexchange.com/questions/44234/how-does-the-extension-of-inboard-flaps-raise-the-effective-critical-angle-of-at

(source: x-plane.org)
What you can see here is that as the slats deploy, the lift coefficient in theory for the same angle of attack remains relatively unaffected. Only the angle of attack at which stall is reached is increased.
This may be sensible because it increases the safety margin before deploying flaps particularly as these will increase drag which if left with the same power setting will increase the angle of attack to maintain the same vertical speed.

While maximum coefficient of lift is higher with flaps (and no slats), as far as I remember the maximum angle of attack is less than clean configuration while your picture still shows slightly more. You are right that slats increase the stall angle of attack in either case.

Been long time since I learned this, but if memory serves me the slats produce more lift for less drag (more "bang for your buck"), whereas flaps are the reverse. On typical airliner (I'm a 767 captain at AAL) slats reduce your stall speed an average of 30 knots.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

authors: Маргарита Лебедева


text:
Why don't helicopter rotors use curved blades? Curved from the top view.
I'm studying blade element analysis and I tried applying it to curved rectangular blades instead of straight ones. It doesn't really show any significant changes in the inflow ratio computation. Why not use curved blades? Is there any reason apart from the obvious problem of increased flapping?

What would the benefit of curved blades be that they'd be used @user31222?

I think this page answers the question in detail  https://aviation.stackexchange.com/questions/8914/why-dont-helicopter-blades-look-like-other-propellers?rq=1

The majority of the length of a blade desn't run in high velocity, hence there's little benefit to swing forward/backward except at the tip.

@GdD for starters wouldn't the surface area be more and hence more lift for same power ?

@user31222 Why do you think you'd get more lift for the same power? Wouldn't you just need more power to drive the bigger blades? And a lot of the extra area wouldn't be perpendicular to the blades' movement anyway.

To a first approximation,  the force on a blade is purely tension along its length, no?  It seems to me that making the blades curved would introduce a bending moment from the centrifugal force, so you'd have to add more mass to resist that moment.  That mass would create more force, so you'd have to make the root stronger, which means still more mass...


text:
Can a Stewart Platform be used instead of a swash-plate assembly in a helicopter? What are the pros and cons?
https://en.wikipedia.org/wiki/Stewart_platform
Also, are there any helicopters in service that use this mechanism?
I was thinking along the lines of using it instead of the part of the swashplate assembly that is used to change the collective pitch.

Swash plates just control individual blade pitch as the blades go around.  Are you thinking along the lines of a Stewart Platform to move the entire rotor disc as a unit like on a gyroplane?

Please edit your question to explain whether you are referring to controlling a swash plate with a hexapod-like construction or tilting the entire rotor head - for now, I voted to close as "Unclear what you're asking". On an additional note, a hexapod controls six degrees of freedom, while you only need three degrees of freedom: pitch+roll (cyclic) and axial (collective).

Very related

Possible duplicate of Why does a helicopter need cyclic control rather than just tilting the whole main rotor?

To replace an effective technology, propose a better technology for that particular application.
The Stewart platform (as shown) would add both weight and complexity, and therefore cost and potential performance limitations, to a function already accomplished with less weight and less complexity.  As @Therac pointed out, tilting the rotor is not necessarily impossible, but this mechanism would not replace the swashplate.

Direct motors or servo flaps can do that, at the cost of requiring
  constantly correcting computer control.

This means that you have to build yet another subsystem to do that: adds weight, adds cost, adds complexity.  Granted, complexity itself is not an "all stop" design consideration (or helicopters would not be flying today :) )
Let's consider the next issue: consequences of failure.  If you put this system into place, what happens when it fails/breaks?  What does the rotor system do, or not do, as a consequence of that?  How are the loads being transmitted through the airframe/flight control system in this case?
The Stewart platform is fit for purpose for a variety of applications (one being motion in a flight simulator) but when it comes to helicopter design, you have to earn your way on to the aircraft in terms of the weight required.  Until you can explain how this system is better than the system that has been shown to work, what incentive is there to apply that?  Given its proposed relationship to the flight controls, which are critical to both function and flight safety, there isn't an incentive readily apparent.

The purpose of the swashplate isn't to tilt the rotor head. It's to pitch each blade as it passes through various sectors of the disc.
In a Stewart platform, both plates rotate at the same time. In a helicopter swashplate, the control plate stays stationary. Rotor blades pass over the stationary plate and sort of follow its profile in pitch.
Tilting the rotor is not necessarily impossible, but it would not replace the swashplate. Direct motors or servo flaps can do that, at the cost of requiring constant correct computer control.

This Wikipedia on Swashplate (aeronautics) indicates

Alternative mechanics to the stationary (outer) swashplate are the hexapod and the universal joint.

So it would seem possible.  Very difficult to find anything useful searching for helicopter & hexapod tho, nothing appropriate is coming up, everything seems to be drones, or using the Gough-Stewart platform as the bed for things like testing.
Physik Instrumente (PI) has  broad line of Stewart Platform motion controllers, my impression is that these look a lot more complex than a swashplate.
There's this paper on Development of swashplateless helicopter blade pitch control system using the limited angle direct-drive motor (LADDM)
which is much more interesting reading.

I have read both the wikipedia article and the LADDM paper. I wanted to know if it would be feasible to use this mechanism in a helicopter to tilt the rotor head and if not why?

@user31222, theoretically everything is feasible, but why? Just think: Stewart platform is a 6-DoF machine, while the swashplate is 3-DoF (plus each needs to pass continuous rotation). It's an order of magnitude more complexity, and what for?

Enstrom helicopters use the Universal (Hookes) Joint design. Control feedback not as well mitigated with this design.


text:
What would be the impact of replacing the engines on the 737 MAX, not just reworking MCAS?
There has obviously been a lot of focus on the MCAS failure following from the 737 MAX crashes. However, the MCAS appears to be a compensating control for design decisions, specifically the replacement of the CFM56-7BE engines on 737NG with the much larger, more efficient LEAP-1B. That in turn necessitated a higher ground clearance.
In lieu of redesigning the landing gear to provide greater clearance (and raising the overall height of the plane), the engine pylon was redesigned, moving the engine further ahead of the wing and closer in line with the wing surface. There were other changes as well.
The re-positioned engines changed the thrust line. The resulting control characteristics were compensated for in software, with the MCAS addressing a very specific negative flight characteristic.
Notwithstanding the new engines being more efficient (resulting in lower operating costs), is it possible and what would be the impact of retrofitting the existing fleet of 737 MAX with an engine and pylon in the previous position ? Could for example, the CFM56-7BE and pylon be retrofitted?
There are plenty of plane models offered with multiple engine configurations, though I imagine they are fit off a similar pylon / housing.
If I were an operator of MAX fleet in which the public has lost confidence in flying on, I'd like some other option than scrapping the fleet. Edit/Addenda: I don't know anyone is planning to scrap the fleet and it's far too early to suggest what the final outcome may be as this story plays out. There have definitely been order cancellations, orders lost and questions surrounding the plane's certification. You can't cancel an already delivered/completed order; it would be difficult to force Boeing to buy them back and replace them (with what?). IF Boeing offered to "retrofit the MAX as an NG-like", it might be the best possible outcome for all.
It certainly seems less drastic than Boeing starting from a completely different base design or losing customers to Airbus.

It wasn't so much the thrust line, which didn't change much (moving it forward doesn't do anything) but the increased and more forward offset cross sectional area of the nacelles that moved the neutral point forward which at high AOAs have an effect somewhat like moving the CG aft.  Probably the simplest physical fix might have been to make the tail bigger so they could move the CG operating range forward.  Would've killed the program though.

Not an aviation engineer, so just going by what I read for"'thrust line has changed". Was trying to describe the engine location is forward and UP, changing the airflow around the wings (plus moving the center of gravity forward - para 9

I haven't heard anything about scrapping the entire fleet... where did you get that idea?

Added context around "scrapping the fleet" remark.

I think when aircrafts has multiple engine offers, all engines have similar characteristics (similar size, similar aerodynamic perturbations,...) thus changing engines do not require aerodynamic nor structural changes.

Possible? Yes.  Economically feasible, not even close.  To re-engine the plane, you would basically have to re-do a large amount of the FAR 25 certification.  Right now, Boeing has to re-do one thing, and it will take a few months.  To re-engine the plane would take several years at the least.  However much money it is losing right now, it is a drop in the bucket compared to the cost of what you propose.

In addition, the new engines you have to buy easily cost ~$50M/aircraft.

Near as I know the answer is no, not without additional changes to the type certificate and it would make more sense to add additional hardware and software fixes to the 737 Max’s flight control software before attempting anything that drastic.  Just a sad part of the bloodletting Boeing is having to undergo for years of bad business practices at BCA.  What they should have done was design and build a clean sheet airplane back in 2011.  But that’s water under the bridge.

Yeah Boeing has claimed that for years but the truth is that firm is flush with cash and could have easily saddled the R&D costs on a clean sheet airplane.  But management has been shifting the BCA business model to a cash flow based as opposed to an innovation company.

I would be very surprised if Boeing doesn't have already detailed plans for a clean-sheet successor to the 737. But to publish them now would be foolish.

It seems all the disadvantages of engines in front of wings become advantages when they are placed behind them, stability-wise.  I wonder if Boeing could let the old MD engineers have the small to midsize designs.  They might prefer the MD80, 90, 717, 727 style, while the "big" Boeing 747, 777x line goes on.

Engines are purchased at the same level as the airframe and are a significant cost.

Yes they can be re-engined to B737NG configuration, while retaining the aerodynamic improvements made. From wikipedia:

The new winglet is 9 ft 6 in (2.90 m) high.[34] Other improvements include a re-contoured tail cone, revised auxiliary power unit inlet and exhaust, aft-body vortex generators removal and other small aerodynamic improvements

Technically possible and with small improvements over the NG, but not including the main benefit of the larger bypass ratio of the LEAP engine. Also not very good for PR.

I guess I don’t see how this quote imdicates a 737 MAX can simply be re-engined and meet 737NG type.

PR at this point is gone, but a smart company may be interested in a lower cost "reworked" model using older engines, particularly as a freighter.  It would be the same thing:  set up a production/salvage line and roll out a saleable product.  Hopefully, with some positive teamwork with "regulators", this could be done.

None of that is going to happen.  There will be a fix and it will be software based one, way or another, however long it takes.  The problem isn't really the pitch behavior problem that MCAS was designed to address; it's the way MCAS and its architecture was designed and certified.
There are even stranger software band-aids out there on other designs.  The 747-8 uses a software based solution for wing "flutter" (more of a vibration/oscillation than flutter) where the tip shakes up and down at 3 or 5 hz or so in certain regimes.  Rather than redesign the wing to increase its torsional stiffness, they use the FBW computer to actively oppose the vibration with outboard aileron inputs (which is normally inactive at this point), transparently to the crew.

This doesn't really answer the question. The OP wanted to know whether it is possible to change the engines not whether Boeing is going to do it.


text:
Why does the 767’s main landing gear appear spaced considerably farther apart than airplanes of a comparable size?
Below is a comparison of the 767, 787, and A350 main landing gear. The larger distance on the 767 also appears to make the airplane lower to the ground.

I think the 767 appears to be lower to the ground because the flaps are deployed, so the landing gear struts look shorter.

The apparent distance on the 767 is also skewed by the fact that the shot isn't directly head-on as it is for the 787 and A320

The Boeing 767 main landing gear is not actually spaced further apart than other twin-engine wide-bodies:

Aircraft
Wingspan
Gear Spacing
Fuselage Width
Gear Spacing:Fuselage Width

B767
48 - 52 m
9.3 m
5.03 m
1.85

B777
61 - 65 m
10.97 m
6.2 m
1.77

B787
60 m
9.8 m
5.77 m
1.70

A330
60 - 64 m
10.68 m
5.64 m
1.90

A350
65 m
10.6 m
5.96 m
1.78

(Data source: Boeing Airplane Characteristics and Airbus Aircraft Characteristics)
As you can see, the 767 has the shortest gear spacing of all of these aircraft. What creates the illusion of a wider spacing, is the much smaller wingspan of the 767 and the smaller fuselage width compared to the others. You said "airplanes of a comparable size" in your question, but they are really not. The 767 is considerably smaller.
What typically determines the needed gear spacing, is the required engine ground clearance, especially when the aircraft is rolling just after takeoff or just before landing.

I think the fuselage width also plays in. From the photos (only), using "1 fuselage diameter" as the unit of measurement, the 767 gear appear farther apart. I think the false assumption of matching fuselage sizes contributes to the OP's misunderstanding.

@RalphJ Good point, I added fuselage width to the table.

Nice addition.  There must be some foreshortening in the photos (767 at long distance vs the others up close, making their fuselages appear wider relative to the gear); from just the pictures I expected more difference in diameters than what these numbers reveal.

Maybe you could add a Gear Spacing:Fuselage Width ratio column to the table?

I took the liberty of adding the column that @Barmar suggested, as I was busy calculating those ratios after reading the answer, but before reading comments. Please feel free to roll back/edit as you see fit.

My thought is that the camera lens is the greatest factor in the illusion of spacing.  The first photo obviously uses a telephoto lens from a long ways down the runway, the other two are wider angle lenses taking photos on the ramp.  This can have a dramatic effect on the perspective.

@Bianfable +1 for Gear Spacing:Fuselage Width ratio :)

I agree with @MichaelHall: it's called Perspective Distortion (https://en.wikipedia.org/wiki/Perspective_distortion_(photography))

The reason why the main landing gear appears to be "narrower" in the second and third photo is Perspective Distortion: when the photographer is standing very close to the airplane, the parts that are closer to them (e.g. the front part of the fuselage, the nose wheel) will appear larger than the parts that are further away (e.g. the main landing gear, including the distance between the left and right gears). If you look closely, you will notice that in the 787 photo, the nose gear tires appear larger than those on the main gear, which they are obviously not. The 767 photo is taken from the other end of the runway with a strong zoom lens, that's why the perspective is "flattened" and all the elements of the airplane are at the same scale. If you look at 787 and A350 images taken from a similar perspective, the landing gear appears spaced further apart:

(By 玄史生 - CC BY-SA 3.0, from Wikimedia)

(By Olivier Cabaret - CC BY 2.0, from Wikimedia)


text:
Have any commercial airline passengers ever been injured from hypoxia due to a depressurization event?
This question is inspired by the question "What can I do to save my life if oxygen masks fail to drop down? Is it possible?" One of my first thoughts upon seeing that question was: do you need to do anything, or will you survive regardless of what you do?
Note that I'm not asking about situations like Helios Airways Flight 522, where the crew became incapacitated due to hypoxia, resulting in a crash which killed all on board. I'm wondering if a passenger has ever gotten hypoxia and suffered from health problems (or death) as a result.

This question is similar: http://aviation.stackexchange.com/questions/2054/would-failure-to-put-on-an-oxygen-mask-during-loss-of-cabin-pressure-result-in-d?noredirect=1&lq=1 But none of the answers state whether or not adverse health effects have actually happened.

The passengers on Helios 522 were incapacitated or died due to hypoxia. Those masks in the aircraft only have enough oxygen to sustain the passengers while the plane descends to a safer altitude, or about 12 minutes. Helios 522 was on autopilot at 34,000 feet for 2 and a half hours. The autopsy showed that the passengers were alive at the time of the crash, but it could not determine if they were conscious. The aircraft was unpressurised at an altitude as high as the peak of Everest, the crew were incapacitated, so it follows that the passengers would have been as well, despite the fact that the autopsy showed that they were still alive at the time of the crash.
Now, let's suppose that they had survived the crash. They were hypoxic for 2 hours, which means they would have suffered brain damage and would be suffering with the long term effects of that (Insomnia, amnesia, etc) as well as injuries sustained from the crash itself.

The question I really meant to ask was: have any passengers been injured due to hypoxia despite the plane successfully making a safe landing? But you answered the question I actually asked, so I'm giving you the accept.

More than 60 people have climbed Everest without oxygen(with one who stayed in the death zone for more than 24 hours). There are no documented cases of brain damage among them. I'm not sure the passengers would have suffered brain damage from just 2 hours in the death zone.

@Retiredaccount: The people who climbed Everest sans oxygen spent months acclimating to high altitudes beforehand to prepare themselves.  The passengers on HCY522 probably did not.

Also, HCY522 was considerably higher than the peak of Everest; said peak is at the approximate equivalent of FL290, while HCY522 was cruising at FL340.

Yes, people have died due to depressurization of commercial aircraft, as well as military.  There was a famous case of a Learjet where everyone became unconscious from a depressurization and the plane kept flying until it ran out of fuel.  A more recent incident, a couple of years ago in a TBM 900 where the plane flew on with the crew and passengers unconscious or dead, until they passed over Cuba and crashed near Jamaica.
In my time as an Air Force pilot I had one explosive decompression, but  as I was in a fighter I already had my oxygen mask on so it was no big deal.  In the B-52 we wore O2 masks during any highly critical phase of flight, low level, air refueling, landings etc. We also had to have helmet on, so mask on or hanging off our face, whenever we were above certain altitudes (can't remember now) or when one pilot left the flight deck.
I had more insidious decompression in my pressurized Cessna skymaster but that was during my air force years so I was used to always checking gauges, and I caught the problem before the cabin altitude went high enough to be dangerous.

I'm not sure I would consider anyone on either of those example flights "commercial airline passengers."

This does not answer (the intented) question: Did somebody get injured or died, while the plane landed successfully. In the Helios case, all were alive, but incapacitated when the plane crashed.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
For A330, why is the DC BAT BUS momentarily supplied for 7 seconds in BAT-only configuration?
For A330, may I know why is the DC BAT BUS supplied for approximate 7 seconds in the BAT only configuration? From the FCOM, during the 7s, the DC BAT is supplied directly by the BAT 1/2 through the BCL charging contactors (6PB1/2, I believe).
Some say it is the time for the CSM/G to speed up. But the CSM/G is to mainly supply DC ESS (through the TR ESS). Even after the CSM/G is speed-up, the DC BAT will not be supplied any more, so it's not that important.
Also, even during the BAT only config, the BAT 1/2 can supply DC ESS directly, so it's not needed to supply the DC ESS through the DC BAT (by the DC ESS TIME Contactor 4PC).
Any people know why is there a 7s momentarily supply? Is it related to some of the equipment connected on DC BAT that it is crutial during the 7s? What makes the DC BAT so important that it is powered only 7 seconds, but not that important after?

From the documentation online, I believe this is the time required to deploy the RAT in case both engines are lost. When the RAT is deployed it pressurizes the GREEN hydraulics powering the emergency generator. In the meantime batteries feed the DC bus which is used to generate AC. Does that make sense?

@mins Not really, that's similar to what someone said for the CSM/G to spool up. If the DC BAT is so important, it should still be powered, by the CSM/G, after 7 seconds, after the RAT deployed and CSM/G spooled up. That means the first 7 seconds by the Bats and the CSM/G will power the DC BAT later. But it's no designed like this. CSM/G will only power DC ESS, not including the DC BAT.
May be I should rephase my question, what makes the DC BAT so important that it is powered only 7 seconds, but not that important after?

My attempt to read this schematics is (when on batteries) DC ESS is fed by the batteries and DC BAT too using BAT contactor during 7s. After 7s DC BAT is isolated from batteries but is now fed by the CSM/G thru TR 1/2 and DC 1/2 buses. Is it correct? If so, DC BAT is always fed unless DC TIE is opened, I don't get the behavior of this switch in this process (sorry for the multiple edits of this comment, I hope you escaped it).

@mins when the CSM/G kicks in, TR1/2 will be (already be) dead and so DC1/2 will also be dead. So DC BAT will no longer be powered after 7 sec,  no matter it's the BAT-only config, EDP driven CSM/G config, or the RAT driven CSM/G config.

I must miss something, AC 1/2 are certainly lost when CSM/G starts, hence TR 1/2 are certainly unpowered, I agree. But I don't see why CSM/G wouldn't repower TR1/2 as soon as it is operational, it's the goal.

@mins um... CSM/G only power the ESSential buses (and the sheddable buses if EDP driven). Not the whole electrical network


text:
Where are the planes going that fly west over Niagara Falls at night?
Where are the planes landing that fly over Niagara Falls, New York late at night heading in a western direction? And what altitude are they flying at? Between 10pm and 12am Wondering if they are going to Toronto ,Detroit or elsewhere . They are commercial flights I think . I did not realize the technical aspect of this site . I was just asking as a point of curiosity and could not find an answer elsewhere .

Welcome to aviation.SE! Are you asking how to identify them (see this question), or have you already identified them but you want to know their flight plan (see this question)? If those questions don't help, please give us as much extra information as possible, e.g. are these airliners or small propeller planes; do they always fly at the same times etc. You might also find the [tour] helpful if you're new to the site.

As explaine din the help center you may rephrase your question to make it more specific.

Go to Flight Radar and you can click on the specific flights and see the plane type and where it is going.


text:
Can I use audio containing Canadian ATC/broadcast radio transmissions in a YouTube video?
I often record my flight training without audio and post some of it to YouTube. I would like to add in audio recording of what I hear and say over the radio as well, but my ground school suggested that it was illegal to make radio transmissions public. On the other hand, I see youtube videos all the time that do include ATC voice traffic.
Can someone clarify for me if it is permissible to record and make public radio transmissions recorded during my own flights?
If it makes any difference, my videos are not/will not be monetized and and my flight training takes place in Canada.
EDIT: finally remembered my source, which is the radio operator restricted certificate study guide, which says:
Radio operators and all persons who become acquainted with radiocommunications are bound to
preserve the privacy of those communications. In accordance with subsection 9(2) of the
Radiocommunication Act, no person shall divulge the contents, or the existence, of communications
transmitted, received or intercepted by a radio station, except as permitted by the addressee of the
message or his/her accredited agent, or to authorized officials of the Government of Canada, officers of
the court or an operator of a telecommunications system as is necessary to forward or deliver the
communication. These restrictions do not apply to a message of distress, urgency, safety or to messages
addressed to “ALL STATIONS” (i.e. weather reports, storm warnings, etc.).
As outlined in section 9.1 of the Act, any person who violates the privacy of communications is liable,
on summary conviction, in the case of an individual, to a fine not exceeding twenty-five thousand dollars
or to imprisonment for a term not exceeding one year, or to both, or, in the case of a person other than an
individual, on summary conviction, to a fine not exceeding seventy-five thousand dollars. https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf01397.html
It sounds like I am able to post radio communications for which I am the addressee (and presumably addressor)

I would not hesitate to do that.  But, this is just a comment, not a real answer.

Ask them to point you to their source. In the USA that's nonsense, but I don't know about Canadian law.  Also, realize that if you did anything that could get you or your instructor in trouble, even without realizing it at the time, a posted video is pretty clear evidence of what happened.  Time can be correlated to ATC tapes.  At a minimum, might want to get your instructor to consent, since it's his ticket on the line if somebody makes a stink about something & an investigator agrees that it's an issue.

@RalphJ fair point, I will do that. Mostly I had planned on posting solo video though.

If you don't get a good answer here you might consider asking on law.SE. Although there's at least one prominent example that shows this is completely legal in Canada.

You can't do this in the UK, but it looks like you can in Canada. LiveATC even has Canadian channels.

Until you get more information, you should assume this is not allowed, as in many countries this won't be allowed. Some years ago, and possibly still today, just listening to ATC wasn't permitted in the UK, unless you were using ATC services. US have another view on privacy (disclosed data can be used by anyone), and are not the predominant model in this area.

Sounds like this might be a question for law.SE after all

If your ground school suggested you not to do it, then do not.
You're better off losing a few views than losing your license.

I don't see how there is any reasonable expectation of privacy with radio broadcast but lawmakers have been known to get absurd notions in their heads. Canada law tends to settle somewhere between the UK and USA in many areas. In the USA recording private comms generally requires consent, but speaking in a manner that can be readily overheard by passive non-participants is not considered private. An office with door closed, telephone call, letter in an envelope, encrypted radio all considered private. Conversation open to a common-use hall at work or non-encrypted radio broadcast are public.

@MaxPower that is certainly the most reasonable way to approach it, but as you say, reasonable doesn't always matter legally

@KBriggs "reasonable expectation" is actually legal terminology, I didn't mean it in the informal manner.

@MaxPower good to know

Thanks for mentioning your edits, and this was a great question to answer especially for a Canadian citizen!

In countries where it is illegal to listen to ATC chatter like the UK, it is also illegal to post it, and you can see this on LiveATC, where you can easily listen to YKZ, YYZ, YVR, YTZ, and YHZ, etc. in Canada, but you can't listen to UK airport feeds or sectors for example LHR, LGW and MAN.
So assuming that liveatc is not an illegal orginization, (we know that for sure because literally the #1 thing that comes up when you search on google atc, liveatc comes up. And if it was illegal, the RCMP would have taken down liveatc at least in canada years ago!) we can say that no, posting atc chatter online is not illegal in Canada.

Is it possible those Canadian transmissions are being recorded and posted by receivers on the United States side of the border, and would that not make the legal ssue much different? Also I know Canadian ATC controls some low altitude sectors of US airspace in NW Washington, due to radar coverage I presume, domestic US flights that never cross the border.

@Max Power: That's like saying the irish people on the other side could be recording UK transmissions or like saying if a foreigner came in and didn't pay taxes it would be legal. Plus, if it was US citizens who were recording the transmissions, then how would we be able to get transmissions from CYHZ? I highly doubt that US frequency scanners would be in range at that point.

The Legal answer is no

Prohibition
(1.1) Except as prescribed, no person shall make use of or divulge a radio-based telephone communication
(a) if the originator of the communication or the person intended by the originator of the communication to receive it was in Canada
when the communication was made; and
(b) unless the originator, or the person intended by the originator to receive the communication consents to the use or
divulgence.
Marginal note:Idem
(2) Except as prescribed, no person shall intercept and make use of, or intercept and divulge, any radiocommunication, except as
permitted by the originator of the communication or the person
intended by the originator of the communication to receive it.
Marginal note:Exceptions
(3) Subsection (2) does not apply in respect of radiocommunication that consists of broadcasting, a subscription programming signal or a
network feed.
1989, c. 17, s. 61991, c. 11, s. 831993, c. 40, s. 24

https://laws.justice.gc.ca/eng/acts/r-2/fulltext.html
In reality, if you are posting simple routine communications Its unlikely any inspector would bother tracking you down, and worst case you would probably get a "don't do it again" letter, an alternative would be to show your calls, then edit out the response.
Edit, upon re-reading, it looks like you may be able to show your communications with ATC, but only yours, "unless the originator, or the person intended by the originator to receive the communication"
Also yes, Live ATC is not really aloud to post radio traffic [they may be legal to rebroadcast in real time], I doubt anyone cares enough to enforce the rules.


text:
Why don't commercial airplanes carry Earth-observing instruments?
Governments and private companies spend hundreds of millions of dollars to send Earth-observing satellites to capture imagery or scan the terrain with lasers or radars.
Meanwhile, commercial planes are constantly flying around the world, and even if they do not offer global coverage, they could still carry Earth-observing instrumentation with almost no additional cost. I'm sure the data they could provide would have many scientific and commercial applications. In some cases they could be even better than satellite observations due to much shorter revisit times, less atmospheric influence and shorter round-trip times for laser and radar signals.
For example, some satellites like IceSat and IceSat-2 were designed to repeat laser altimetry observations over the same ground tracks over and over. With much interest in Greenland, the icefields in Yukon/Alaska and Antarctica. Again, in this case, commercial flight could provide very good coverage of the first two areas of interest at a fraction of the cost.
I'm a glaciologist working on the Patagonian icefields, where the persistent cloud cover renders most of the images captured by Earth-observing satellite useless. I'm evaluating the possibility of contacting authorities and airlines to collaborate in a project to put instrumentation on the planes that overfly the icefields several times a day. However, I'm sure that I'm not the first with this idea of putting instruments on commercial planes. Thus, I'm surprised that no commercial airplanes carry Earth-observing instruments.
Therefore my question:
Is there any insurmountable technical or legal limitation to equipping commercial airplanes with Earth-observing instruments?

I doubt the "no additional cost" thing. A system for ground observation has to be integrated into and powered by the plane's systems. Thus it is a maintenance relevant - and might even be flight security relevant - component (it has to be installed on the plane with a direct line of sight to the ground) that does induce extra cost for no benefit for the airline.

@Adwaenyth Well, the same entity that would otherwise have sent up a satellite could presumably pay the airline for the extra expense from the money saved by not having to launch and operate a satellite. So that particular downside could presumably be offset pretty easily, if the will to do so is there. (Satellites are not cheap.)

"persistent cloud cover" ... "instrumentation on the planes that overflight the icefields" This isn't an answer, but it's an issue you definitely would want to consider: Commercial airplanes typically fly above the clouds. So if there's a cloud cover, and you are working in the visual part of the spectrum, you are unlikely to get much better data from airplane-mounted equipment than from equipment in Earth orbit. (Though when conditions are favorable, you might be able to get higher resolution.)

@aCVn well you'd have to compare the costs for building, launching and operating a satellite covering most of the earth surface to having a myriad of contracts with different airlines collecting, storing, managing and unifying the data for a rather limited surface area. It's not only the cost for the satellite itself but also for the total overhead if you have such a widespread system. It's not like pressing a single button and having all the data in one system for analysis. At airlines it probably affects the daily routine of thousands of people and that costs a lot of money.

@Adwaenyth Sure, I'm not saying it's a trivial undertaking; I'm just saying that you can't say that since there's a cost to doing it by cooperation with airlines, that doing it by satellite monitoring is necessarily cheaper. There's a different set of costs, which may total up to doing it by aircraft costing more or less than doing it by satellite (but a more detailed analysis would be needed to know which).

How would your instruments look at the ground?  All the windows look sideways, and passengers want to look out of them anyway.

@aCVn "persistent cloud cover" - the OP may just be hoping that with enough overflights he gets more chances of usable data.

They probably already do carry such instruments, to help the pilots know when to to turn on the chemtrail generators.  Of course everyone in the aviation industry is sworn to secrecy and will deny this.

Operating a commercial service while also carrying equipment serving an intelligence gathering or espionage role would certainly introduce legal complications.  Many destination countries would not generally be happy about foreign carriers spying on their country.

Not an unsurmontable issue, there are places such as the Embraer R-99 which carry an EO instrument, and at least could fly some passengers and land on commercial airports. If memory serves me right, this is a military plane, whose radar cost more than the rest of it altogether. It would be really messy from a business point of view to secure the funds/demand to justify the case for acquiring one such model.

@aCVn Thanks for your comments. And Martin Bonner is totally right about my point. Frequent overflight would just increase the chances that some imagery is captured during the brief spells of good weather and clear skies.

@MartinBonner The instruments would need to be mounted on the belly of the plane. It won't be supper easy tu put them there, but much easier than putting them in orbit. There are many dedicated planes for surveying, and they do have instruments poking out of the bottom of the plane.

@CamiloRada there are already dedicated companies that do such things. Most high resolution images on google earth are in fact from small planes and not satellites. Oil companies frequently contract such people for photography/lidar of interesting regions. Probably airline companies are not that interested in competing in a new industry all of the sudden.

If you put the instruments on the belly of the plane, that is going to affect the aerodynamics.  You will have to pay for the additional fuel, and I wonder how it will affect the certification.

"commercial" flights are not solely "passenger", it could mean "cargo" aircraft which may be easier to arrange.

One thing to note about the OP's situation: Although many planes may fly over the same area regularly where the OP wants to have aerial observations, there is no guarantee that those are the same physical aircraft flying over each time.

They do! Well, at least some of them. There is for example a project called TAMDAR (Tropospheric Airborne Meteorological Data Reporting) that e.g. Icelandair is a part of. There is a document published by the Icelandic Meteorological Office about it.
Another example is MOZAIC/IAGOS: Atmospheric Research Using Commercial Airliners.

More broadly, the AMDAR program does this on a worldwide basis with participating airlines and national meteorological agencies. The advantage is that it works using pressure and temperature sensors that are already factory equipment on airliners, along with the communications equipment typically available, so the costs are fairly minimal (and there's some benefit to the airlines, as anything that helps weather forecasters can help them). More complicated special-purpose sensors would be quite expensive and a much harder sell.

I would not call that "Earth observing instruments".

@VladimirF now I looked up the definition of "Earth observation" on Wikipedia and the first point is "Earth observations may include: numerical measurements taken by a thermometer, wind gauge, ocean buoy, altimeter or seismometer"

@Vladimir Well, ya see there's Earth, the planet and earth, the stuff we stick seeds in. Capitalization can sometimes be important.

http://flyht.com/flyhtweather/

I work in the aviation industry, specifically repair, maintenance and engineering. While not an engineer myself, I work alongside them.
Adding anything to an airframe, internally or externally, always has a cost in time, materials and funds. Our company is in the process of modifying ERJ regional aircraft with seatside electrical outlets for passenger access. The project manager and our electrical engineer have each spent over 200 hours designing the controls and wiring for the mod, procuring materials and consulting airframe engineers. Our inspectors have consulted with the FAA to have the mod approved. Our structures and interior technicians have designed and produced new panels inside the cabin, and our electricians have installed the controls and wiring.
This project has cost our customer roughly half a million dollars, and this figure does not take into account the inevitable oversights that arise in any engineering project. These additions to the airframe must be carefully considered against the aircraft total weight and the balance on each axis of control. Now add in training time for aircrews to be aware of the mods and how to handle issues.
Your proposal will necessarily cost at least this amount, and may not be feasible if the equipment is too heavy or bulky. In light of the other comments, I conclude that this will never fly. However, the military might be tasked with this kind of job, as they already have dedicated surveillance aircraft.
Good luck in Patagonia.

Hi Dan, it is very interesting to hear an opinion from an insider. Thanks! that helps. However, it is still unclear to my why the economical benefits of having power outlets on the sear outweighs so clearly the benefits that could be obtained of selling imagery and terrain data for aglriculture, map providers (like google maps, here, etc.), mining, etc. All those industries currently spend millions of dollars in products that could be acquired from comercial airliners. I'm sure companies already made the cost benefit math, I wonder what makes Earth Observation such a bad idea for airlines,

@CamiloRada, as you note in your question, coverage by commercial aircraft is limited, though the re-visit time is pretty good.  Commercial imagery providers get more value from having large-area coverage than they do from re-visit frequency, so the better value-for-money option is to run their own fleet of dedicated aircraft with low-frequency visits to each area.

"Adding anything to an airframe, internally or externally, always has a cost in time, materials and funds." And fuel! Anything that has mass requires fuel to fly in an airplane. While satellites requires massive amounts of fuel to get to orbit, they require virtual no fuel once on-orbit. The same is not true for aircraft. To the airlines (or any other operator of airplanes) weight = money.

Of course it has a cost.  I'm sure scientists would gladly pay for that, as the cost is just a tiny fraction compared to launching a satellite or even compared to flying their own dedicated research aircraft.

And in addition to the cost of installation there's the cost of maintenance, certification, and operation.

The added equipment also subtracts from the total MTOM so the plane can carry less freight - whether associated with a passenger on board or a separate paying customer. If the EO equipment is installed in any sort of external fairing, that causes drag which increases the fuel requirement which increases the fuel carried which increases the cost.

Aside from the issues of weight and complexity, there are potential legal and political considerations regarding commercial carriage of certain kinds of observational equipment. Korean Airlines Flight 007 was shot down by a Soviet interceptor in 1983 when it inadvertently flew over Soviet territory leading the Soviets to believe it to be a military reconnaissance aircraft. Equipping commercial aircraft with photographic or laser-based earth observation instruments--even if meant to measure ice, water, clouds, or topography--could be seen as potentially hostile, leading to an elevated risk of civilian casualties.
It wouldn't have to be a shoot-down, either: a forced landing and detention of the passengers would make people much less likely to fly that airline. At a minimum, airlines might have to change routes around politically sensitive areas, leading to increased costs, even if only a few aircraft were so configured.
While major powers such as the US, Russia, and China would be unlikely to undertake excessively hostile action, one cannot always predict what a smaller nation might do.

This makes a lot of sense, and is the best explanation I found so far. Still doesn't explain why is such a bad business to do it on domestic flights. I mean, within the US borders agriculture, map providers (like google maps, here, etc.), mining, and other industries spend millions of dollars on imagery and terrain data that could be acquired from comercial airliners. I'm sure companies already made the cost benefit math, I wonder what makes Earth Observation such a bad idea for airlines.

@CamiloRada in this scenario, adding the equipment makes the aircraft only usable flights that remain in domestic/international airspace. This makes the airline less flexible. The other option is to go to the additional cost of making it modular and taking it out when not allowed.

I would say the opposite. After 2001, It is more likely to be big nations rather than small nations who are worried about anything remotely related to airplanes security.

The Soviet shootdown of KAL007 greatly raised tensions between the US and the USSR at a time when tensions were already high. They contributed to the Soviets nearly launching World War III during Exercise Able Archer 83. As such, major powers are typically more careful to identify aircraft before shooting at it, Malaysia Flight 17 and Iran Air Flight 655 being major exceptions. In certain unstable areas, leaders can get trigger-happy and shoot at aircraft (usually smaller planes) on rumors. It happens often in Africa and has happened elsewhere, and could easily happen again.

Is there any insurmountable technical or legal limitation to equip
  commercial airplanes with Earth Observing instruments?

This question would probably be better answered on space.se, by people who know what are the advantages of a satellite over an aircraft and the reasons why missions are not conducted on aircraft.
However several aspects indeed differ between a satellite and a commercial plane, three come to mind:

The practical area visible for a given field of view: At 400 km altitude (low end of the low earth orbit) the area covered is much larger than at 10 km.

You can have an idea by comparing what you can view through a camera on each side of a given object, when this object is at 10 m and at 400 m.

Depending on the mission this can be decisive.

The degree and frequency of vibrations: Usually, when out of the atmosphere, a satellite is very stable. A plane shows a lot of (comparatively) large amplitude vibrations due to the engines and the aerodynamic pressure, especially at high frequencies.

This is not a trivial problem, because at 10 km you usually need a very long focal length (or a very small aperture radar array), and the effect of the vibrations is directly proportional to the focal length.

Large sensors used for good definition and contrasted shots also increase the effect in proportion of their diameter, because if the diameter is twice, the focal length must be twice to maintain the field of view (that's why digital cameras with small sensors have short lens).

What can be seen as a simple problem on Earth with a 50 mm lens and a full size sensor, is actually a serious one when surveying at 10 km.

A stabilization mechanism will be required (e.g. inertial platform, or mirror/lens/aerial dynamic correction). However those mechanisms need expensive maintenance and/or calibration to be effective.

No airline will allow repetitive maintenance windows for that. Even when paid, this won't be comparable to passenger tickets, cargo fees and on-board sales. Airliners are not, for this aspect, comparable to spy aircraft and dedicated surveying aircraft.

Aircraft also experience permanent roll, pitch and yaw changes, but as they are relatively slow they are easy to counter with a simple stabilized platform.

Area coverage: Airways are very small corridors in the sky, at specific locations.

In contrary satellites in low orbit (which are therefore not geostationary) see the Earth rotating below them and cover easily most of the planet area (specially polar orbit ones).

Regarding the cloud coverage preventing satellite observation, the problem will be nearly the same for an airliner. It flies above the clouds, even if polar routes are lower due to the tropopause being closer to the ground.

Hmmm. But the question is not about the differences between satellite capabilities and aircraft-based capabilities. It’s about technical and legal limitations of the working with airlines. Thus, this network is more appropriate than the space.se network.

I get your points. But you can build another even longer list of the difficulties of operating and instrument from a satellite in contrast to an airplane. The cost of the down time that an extra system might require is an interesting one.
Also, regarding to coverage, many satellites don't have storage capacity and can only rely information back to earth when they are over a ground station. Therefore, they can only really observe the terrain around the ground station. For a long time brazilian, indian and corean satelites were ony observing their own countries. Still they sent a satellite.

In contrary satellites in low orbit (which are therefore not geostationary) see the Earth rotating below them and cover easily most of the planet area (specially polar orbit ones)., that's not necessarily accurate for most Earth observation satellites.  A radar on a sun-synchronous satellite such as Cloudsat, has a narrow swath width (~1 km) and a repeated ground pattern, so it doesn't see the entire world either.  It's true for passive sensors, and although satellites do reach all regions of the world, nadir-looking active sensors do not easily cover the entire planet.

@gerrit: I agree partially, the fact an instrument works with small field of view doesn't mean the vehicle is not able to overfly (zenith) the whole area between latitudes allowed by the inclination. Two consecutive bands may not overlap though. E.g. Sun synchronous Terra.

@mins In theory, yes — but it'd have to be commanded to overfly a specific spot for an instrument with a narrow swath width to observe it.  I don't know how precise they can hit it (question for [Space.SE]), the swath width of the CALIOP LIDAR is less than 100 metre.  I don't know if this type of commanding happens with scientific satellites, though (it certainly does with commercial Earth observation satellites).

For comparison between aircraft and satellite in general, you may search for atmospheric satelite here.

Space fan here, and I think you are underestimating the size of the task.
Earth has a surface area of 510 million km2.
A plane travelling at 500 km/h with a 10 km observation track can cover 5000 km2/h, or 50000 km2 per 10 hour operational day, ignoring transit to/from nearest available airport. It would need approximately 10,000 days (28 plane-years) to cover the surface of the earth. I'm not sure what the cost of operating say seven crewed planes throughout daylight hours for four years is, but I'm sure it adds up, even for a small plane. With a crew of two, we're looking at 56 pilot-years of salaries (assuming they work 10 a day hours seven days a week and never have time off!) which is running into the millions already, before you even consider fuel or maintenance.
In contrast, SpaceX publish their prices and you can charter a Falcon 9 for $62 million to put 22800 kg into low earth orbit. Your satellite only weighs 2280 kg? No problem, rideshare deals are available, so your budget would be around 6.2 million plus a markup. Just wait for a near polar rideshare (such as the SSO-A mission scheduled to launched on 3 December 2018) and once in orbit your satellite will travel at around 30000 km/h, completing three laps of the earth every four hours. The earth's circumference is 40000 km, so with a 10 km track you should be able to cover the whole equator in 4000 laps, which is 5333 hours. Accounting for day/night the job should be done in under two years with a single satellite.
As discussed in other answers, planes are an option for small areas of particular interest, but just as satellites suffer from cloud obscuration, so can planes be affected by the weather, either by obscuration or by being grounded due to unsafe conditions.
While putting equipment on existing commercial flights is an interesting idea, if the flights follow the same route on a regular basis, only the areas on common flight paths would be mapped, which may or may not coincide with areas of interest.

Can you add a reference to "SSO2"? E.g., is it related to SSO-A?

@PeterMortensen the most stable reference going forward is most likely https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_Heavy_launches . That said, this particular mission has suffered numerous delays, probably due to the number of parties involved, and I thought it best to wait until after launch to edit it in, in case the date changed again. It would seem the correct designation is indeed SSO-A not SSO2.

OP did not ask for global coverage, but asked for coverage of the Patagonian Icefields.  Unfortunately for OP, not many commercial airliners fly over there either.  As for rideshare; cubesats are too small to carry radars or lidars.

A major reason would be that Earth Observing systems are large, and would take up a significant portion of the interior space of the airliner, space that the company wishes to sell to passengers. they are also heavy, which would impact the range of the plane and trip and drive up fuel costs.
Additionally, airliners want to get from airport to airport as quickly as possible, whereas in observation missions you want to get as many passes over important areas at specific altitudes as possible.
NASA flies many airborne missions every year specifically for earth observations. Some of these are simply proving future satellite sensors, but many more are purely for gathering data on a specific parameter. They utilize their own aircraft though, because the aircraft typically need to be specially modified for the equipment, specifically with portholes cut in the belly of the frame and they then dont have to compete with the needs of a passenger service when it comes to route.

Well, EO systems are not that large anymore. Every kilogram put into orbit cost a lot. So many last generation satellites are the size of a minifridge or smaller.
The point of airlines wanting to go from airport to airport as quick as possible makes  a lot of sense. But for instance, within the US borders coverage of commercial flights would be good, and in the US, agriculture, map providers (like google maps), mining, and other industries spend millions on imagery and terrain data that could be acquired from comercial planes. I wonder what makes Earth Observation such a bad idea for airlines

@CamiloRada No, the coverage would be very poor. The USA only has about 5,000 commercial airports with paved runways. Most of those 5,000 have flights to fewer than 10 other destinations, and many have only one commercial route, to the nearest large airport.  In other first world countries (Canada, for example) the coverage would be even sparser.

Almost every morning, at almost the same time while I wait for the bus to work, there's an air plane that flies overhead. It always come from the same direction, always disappears in the same direction and if you drew a line where it flew those lines would probably probably be pretty close together, if not almost completely overlapping. If you check any website that tracks flights you will likely see that there are specific routes which a lot of planes fly.
Why am I saying this? Because it means that while the idea sounds good, the actual coverage that you get would be pretty small. Multiple planes will record the same data each day and they will record the same data day after day. There will only be a small amount of original data and a whole lot of duplicate data.
You'd be better off only installing the necessary equipment in a few planes that are specifically tasked with recording data. They will get a larger coverage, go where you want them and not record a dizzying amount of duplicate data.

This may not be a problem, if you find a route that happens to overfly the area of interest (OP is interested in Patagonian icefields), the cost of paying an airline sufficient money to convince them to put an instrument on their plane may still be much less than the cost of (regularly!) flying a research aircraft in the same region.

During the Cold War airliners did in fact sometimes carry cameras... but covertly, for intelligence purposes. In particular Aeroflot was known for this, but also "other national airlines" according to this article from 1981: https://www.upi.com/Archives/1981/11/21/US-intelligence-experts-say-Soviet-Aeroflot-airliners-regularly-carry/2330375166800/

It was also done from US airliners flying from west Germany to west Berlin when over the area of east Germany.

In short, airliners and some other civilian aircraft have carried earth observing cameras.  In the 1960's most programs were reduced.  The increased use of satellites was a major factor.  Additionally, at that time, and prior to, airliners tended to fly rather predictable routes, and ATC most countries would route airways and clear planes avoiding targets of interest.
There are numerous open and classified payloads which have been operated since WWII.
Furthermore, there are practical issues in that an aircraft covers a limited area, and scheduled carriers have no real control over their flight times.  So cloud cover and lighting were major issues.
In addition to EO/IR observers, there were SIGINT packages which were used, and are now largely replaced by satellites.
Many survey aircraft have a variety of sensors, such as magnetometers, lidar and other instruments.  However, they are deliberately flown. Your question implies the use of sensors which are not incidental to the primary purpose of the flight.
However to address the question, there are not insurmountable technical issues with aircraft based sensors.  The political/legal issues are varied.  For example, over polar regions significant territorial claims are virtually non-existent.  Flying over Area 51 would pose some governmental limitations.

Many carriers lease their aircraft from holding companies that would obviously forbid making novel changes to the airframe. Even for aircraft owners, cutting a hole for cameras could substantially impact the resale value.
Insurance would have to approve the changes. They're not going to pay a claim for an experimentally-modified aircraft
if anything went wrong with the equipment causing the pilot to declare an emergency, it would negatively impact the entire airline. So even if it was profitable to sell the sensor data, nobody would want to be the first to do it.
Who is going to maintain the equipment ? Now you're talking about retraining ground maintenance crew or adding new ones.
Equipment malfunctions could delay revenue-generating flights. If they prioritize pax over equipment to stay on schedule, then they're carrying dead-weight.

To measure ice field depths and such you must know the actual position of the sensor with greater accuracy than the precision you need for the final measurement. With a satellite ballistically orbiting the earth, that's easy. With a commercial aircraft flight, that's far more difficult, especially including pitch/yaw/roll effects between the GPS, the INS and the sensor.
Further, while adding a sensor to a satellite and orbiting same is very expensive, doing so for a vast fleet of airliners may well be even more so, especially when that includes paying the airlines for the privilege of doing so, including the ongoing maintenance that satellites don't need (they seldom need washing, etc.).

For height measurement, lack of accuracy in position knowledge is definitely a good point

That is true, but it is a solved problem. All the surveying software currently use for UAVs (aka drones) acquired data deals with those issues with no problem, basically using correlations within the data and some ground control points.
The cost of equipping planes with the instruments is a good point. But I'm not sure if it is the only or main factor.

The answer to both your questions is money.  With enough of it these two things are indeed possible.  But, I think your question lacks enough precision to give you a valid, usable answer.
I looked up this Patagonian icefields area that you are studying on 247 flight radar.  Commerical flights barely fly over your area of interest and when they do it's odd curved flight paths let alone changes in altitude.  That's a lot of image pre-processing time to to verify that images taken at different times can be spatially correlated to each other.  Not to mention the fact that you won't get full coverage.  You note clouds being an issue, you won't necessarily get any useable data just by flying underneath them.  Other than sensors like LIDAR, most sensors pick up reflected radiation.  So sure, if you are using an IR sensor and flying over places like volcanoes you can get usable data.  But you might not be so lucky if you sensor relies on reflected light from the sun.
Creating the sensor you want and placing in on a "Vehicle" are just engineering problems.  The hard part, which I know your question left out, is how are you going to store the data, how are you going to retrieve the data, who is going to all of the data collection, where in the world are you going to host it?
I guess if you are looking for free or near free data sets, remember tanstaafl.  If you've been using Landsat, TERRA, AQUA data for your studies these projects were paid for and continue to be paid for by the US government.  Heck it's only been since December 2009 that you could get Landsat for free.  Prior to that I believe is was around $500 US per image that only covers 170 km north-south by 183 km east-west.
I have a feeling you'd be better off finding local pilots to fly your sensors across your icefields and collection the data directly from them.  It won't be cheap, but I'd hazard it would be cheaper than what you are asking for in the long run.
I can't say were I work since I'm not a "spokes person" but I've had about 18 years worth of operations experience in a part of the EOS field.

I disagree with that "flights barely fly over your area". I've looked at flight radar too. And I've travelled hundreds of times from Santiago (SCL) or Puerto Montt (PMC) to Punta Arenas (PUQ) and every flight pass over or just beside the icefilds. I've installed mane reapeat photography cameras (aka time-lapses) in different glaciers. Those systems have the size of a small suitcase and can take pictures autonomously for over a year. You could easily implement wireless data download. Just a camera system like those attached under the commercial planes would yield extremely useful data.

I can provide some insight as an aircraft structures & stress engineer as well as private pilot. From the engineering side of things, this would require a very costly design and installation process. As others have mentioned, weight would need to be factored in for post-mod aircraft operations. Also would require a great deal of stress analysis, certification red tape, testing and possible aerodynamic re-analysis depending on the type of equipment installed. There would also be a major cost for the observation equipment alone. Anything you install on an aircraft as permanent equipment costs MUCH more than what that same electronic or camera device costs if you were to purchase it for use in some other industry. Electronic equipment for aircraft must meet thorough certification and test requirements, which adds enormous cost. As an example, a typical 21" LCD monitor was around 20k dollars last time I checked. And this isn't even the latest and greatest resolution that you'd get buying the same size monitor for $400 at Best Buy. All that extra cost is testing and certification to meet stringent regulatory requirements.  Can the airline justify this cost and recover it in a timely manner by selling imagery? I highly doubt it.
From the pilot side of things, you need to consider that most commercial airliners are going from airport to airport, flying the same patterns over and over. Yes you can see a great deal from 40k feet, but nothing like you can at the altitude of a satellite. There is going to be a large amount of terrain that doesn't get photographed very often, if ever, and the airlines aren't going to burn additional fuel and increase route time to go out of their way to do this. Just my 2 cents.

very costly, sure, but not very costly compared to a satellite design+launch or the use of a dedicated research aircraft.

There are a few issues with your premises.
The cost is not minimal. A National Geographic article gives a cost of roughly 33 cents for 5 pounds per flight.  GOES-16 (NOAA weather satellite) without fuel weighs in at right about 6300 pounds. We can get rid of some of that, but the sensor suite surely will still be quite heavy. Likely costing over $100USD per flight.
Just for perspective, two GOES satellites take images of the entire continental US every five minutes. To get anywhere close to that, pretty much every plane would need to have a sensor suite.   The sensor suite cost and maintenance need to be factored in for all these extra sensors. Even with all the flights in a day you won't get full coverage. You also risk losing data collection when weather conditions ground planes.

The GOES satellites may cover the entire United States, but they've got lousy resolution: 500 meters per pixel at best.  To put that in context, there are entire small towns that won't show up on GOES imagery.

The point isn't the resolution. It's that they have 100% coverage every five minutes. The airlines will get an insignificant percentage and infrequent revisits. At a cost of putting sensors in 1000s of planes.

I'm not suggesting that EO systems on comercial planes can replace GOES or MODIS. I'm just pointing that the data that could be captured from commercial planes would have a great scientific and commercial value, and I not sure why that potential haven't been exploited. I gave the example of some satellites like Icesat and I can add all he WorldView ones, for which EO systems on commercial planes could produce similar data with reduced coverage but also reduced cost.

I believe it's entirely cost. Weight and modifications to the plane would make it expensive. Most sensors would need an unimpeded view. External sensors would impact fuel efficiency. Internal sensors would need to be mounted so it can "see" the earth. That likely means modifying the hull.

I'm very surprised that not a single answer to this question mentioned the magical keywords radiosonde and weather balloon.
Answer: no, there isn't, and as some of the answers noted, some commercial airplanes already do that.
To initialize numerical weather prediction (NWP) model, you need to know the temperature, pressure, relative humidity and winds at every single point of the atmosphere of planet Earth. Okay, we approximate a bit to avoid an infinite amount of data: the atmosphere of planet Earth is divided to small boxes and each box has a single value, assumed to be approximately valid for the entire box. That's a lot of initialization data, and a lot of it are far above the ground in the upper atmosphere.
Currently, weather forecasting is partially based on weather balloons, that are released at periodic times from certain locations. It's definitely possible to augment the information obtained from weather balloons by aircraft measurements. There are probably more airports than weather balloon release points, and airplanes are taking off more frequently than weather balloons are released. Thus, it's greatly beneficial to augment the information of weather balloons by aircraft measurements.
The cost is a non-issue. The weather balloons use radiosondes that are single-use devices. Install one in an airplane, and suddenly it's no longer a single-use device. The fact that these radiosondes can be frequently (many times per day) released for a single use, demonstrates that cost of installing one in an airplane is a non-issue.
The reason this information is needed is that ground-based measurement stations measure only winds, temperature, pressure, etc. at ground level. For numerical weather prediction (NWP), you need measurement data from the entire atmosphere of planet Earth. It's not enough to measure data at ground level, because the NWP model is a model of the entire atmosphere.
However, airplanes will not and cannot replace meteorological satellites. Geostationary satellites see half of the entire Earth continuously and can transmit cloudiness / temperature / etc. data at so short intervals that they are extremely useful in numerical weather prediction. A single airplane, being very close to Earth, sees only a small part of Earth. You cannot have continuous 100% coverage of Earth by merely using airplanes.
Thus, airplanes can be at most replacement for weather balloons. They will not replace satellites.
I can see a world where single-use radiosondes in weather balloons are replaced by multi-use radiosondes in aircraft for economical (too much $$$ to build and discard lots of radiosondes) and ecological (single-use prohibited) reasons. But I cannot see a world where meteorological satellites are completely eliminated. There is a reason why meteorological satellite data is the most important input for NWP.

This is somewhat missing the point.  OP is interested in monitoring icefields, which is orthogonal to radiosondes / weather balloons.  OP could launch a research balloon with equipment attached, but that's not very practical for observing icefields.  And airlines do already feed information back to NWP, not instead of radiosondes, but complementary (of course, NWP is hugely important for airlines too).

authors: Vladimir F Героям слава